tools/testing/selftests/x86/ptrace_syscall.c

   1 #define _GNU_SOURCE
   2
   3 #include <sys/ptrace.h>
   4 #include <sys/types.h>
   5 #include <sys/wait.h>
   6 #include <sys/syscall.h>
   7 #include <sys/user.h>
   8 #include <unistd.h>
   9 #include <errno.h>
  10 #include <stddef.h>
  11 #include <stdio.h>
  12 #include <err.h>
  13 #include <string.h>
  14 #include <asm/ptrace-abi.h>
  15 #include <sys/auxv.h>
  16
  17 /* Bitness-agnostic defines for user_regs_struct fields. */
  18 #ifdef __x86_64__
  19 # define user_syscall_nr        orig_rax
  20 # define user_arg0              rdi
  21 # define user_arg1              rsi
  22 # define user_arg2              rdx
  23 # define user_arg3              r10
  24 # define user_arg4              r8
  25 # define user_arg5              r9
  26 # define user_ip                rip
  27 # define user_ax                rax
  28 #else
  29 # define user_syscall_nr        orig_eax
  30 # define user_arg0              ebx
  31 # define user_arg1              ecx
  32 # define user_arg2              edx
  33 # define user_arg3              esi
  34 # define user_arg4              edi
  35 # define user_arg5              ebp
  36 # define user_ip                eip
  37 # define user_ax                eax
  38 #endif
  39
  40 static int nerrs = 0;
  41
  42 struct syscall_args32 {
  43         uint32_t nr, arg0, arg1, arg2, arg3, arg4, arg5;
  44 };
  45
  46 #ifdef __i386__
  47 extern void sys32_helper(struct syscall_args32 *, void *);
  48 extern void int80_and_ret(void);
  49 #endif
  50
  51 /*
  52  * Helper to invoke int80 with controlled regs and capture the final regs.
  53  */
  54 static void do_full_int80(struct syscall_args32 *args)
  55 {
  56 #ifdef __x86_64__
  57         register unsigned long bp asm("bp") = args->arg5;
  58         asm volatile ("int $0x80"
  59                       : "+a" (args->nr),
  60                         "+b" (args->arg0), "+c" (args->arg1), "+d" (args->arg2),
  61                         "+S" (args->arg3), "+D" (args->arg4), "+r" (bp));
  62         args->arg5 = bp;
  63 #else
  64         sys32_helper(args, int80_and_ret);
  65 #endif
  66 }
  67
  68 #ifdef __i386__
  69 static void (*vsyscall32)(void);
  70
  71 /*
  72  * Nasty helper to invoke AT_SYSINFO (i.e. __kernel_vsyscall) with
  73  * controlled regs and capture the final regs.  This is so nasty that it
  74  * crashes my copy of gdb :)
  75  */
  76 static void do_full_vsyscall32(struct syscall_args32 *args)
  77 {
  78         sys32_helper(args, vsyscall32);
  79 }
  80 #endif
  81
  82 static siginfo_t wait_trap(pid_t chld)
  83 {
  84         siginfo_t si;
  85         if (waitid(P_PID, chld, &si, WEXITED|WSTOPPED) != 0)
  86                 err(1, "waitid");
  87         if (si.si_pid != chld)
  88                 errx(1, "got unexpected pid in event\n");
  89         if (si.si_code != CLD_TRAPPED)
  90                 errx(1, "got unexpected event type %d\n", si.si_code);
  91         return si;
  92 }
  93
  94 static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
  95                        int flags)
  96 {
  97         struct sigaction sa;
  98         memset(&sa, 0, sizeof(sa));
  99         sa.sa_sigaction = handler;
 100         sa.sa_flags = SA_SIGINFO | flags;
 101         sigemptyset(&sa.sa_mask);
 102         if (sigaction(sig, &sa, 0))
 103                 err(1, "sigaction");
 104 }
 105
 106 static void setsigign(int sig, int flags)
 107 {
 108         struct sigaction sa;
 109         memset(&sa, 0, sizeof(sa));
 110         sa.sa_sigaction = (void *)SIG_IGN;
 111         sa.sa_flags = flags;
 112         sigemptyset(&sa.sa_mask);
 113         if (sigaction(sig, &sa, 0))
 114                 err(1, "sigaction");
 115 }
 116
 117 static void clearhandler(int sig)
 118 {
 119         struct sigaction sa;
 120         memset(&sa, 0, sizeof(sa));
 121         sa.sa_handler = SIG_DFL;
 122         sigemptyset(&sa.sa_mask);
 123         if (sigaction(sig, &sa, 0))
 124                 err(1, "sigaction");
 125 }
 126
 127 #ifdef __x86_64__
 128 # define REG_BP REG_RBP
 129 #else
 130 # define REG_BP REG_EBP
 131 #endif
 132
 133 static void empty_handler(int sig, siginfo_t *si, void *ctx_void)
 134 {
 135 }
 136
 137 static void test_sys32_regs(void (*do_syscall)(struct syscall_args32 *))
 138 {
 139         struct syscall_args32 args = {
 140                 .nr = 224,      /* gettid */
 141                 .arg0 = 10, .arg1 = 11, .arg2 = 12,
 142                 .arg3 = 13, .arg4 = 14, .arg5 = 15,
 143         };
 144
 145         do_syscall(&args);
 146
 147         if (args.nr != getpid() ||
 148             args.arg0 != 10 || args.arg1 != 11 || args.arg2 != 12 ||
 149             args.arg3 != 13 || args.arg4 != 14 || args.arg5 != 15) {
 150                 printf("[FAIL]\tgetpid() failed to preseve regs\n");
 151                 nerrs++;
 152         } else {
 153                 printf("[OK]\tgetpid() preserves regs\n");
 154         }
 155
 156         sethandler(SIGUSR1, empty_handler, 0);
 157
 158         args.nr = 37;   /* kill */
 159         args.arg0 = getpid();
 160         args.arg1 = SIGUSR1;
 161         do_syscall(&args);
 162         if (args.nr != 0 ||
 163             args.arg0 != getpid() || args.arg1 != SIGUSR1 || args.arg2 != 12 ||
 164             args.arg3 != 13 || args.arg4 != 14 || args.arg5 != 15) {
 165                 printf("[FAIL]\tkill(getpid(), SIGUSR1) failed to preseve regs\n");
 166                 nerrs++;
 167         } else {
 168                 printf("[OK]\tkill(getpid(), SIGUSR1) preserves regs\n");
 169         }
 170         clearhandler(SIGUSR1);
 171 }
 172
 173 static void test_ptrace_syscall_restart(void)
 174 {
 175         printf("[RUN]\tptrace-induced syscall restart\n");
 176         pid_t chld = fork();
 177         if (chld < 0)
 178                 err(1, "fork");
 179
 180         if (chld == 0) {
 181                 if (ptrace(PTRACE_TRACEME, 0, 0, 0) != 0)
 182                         err(1, "PTRACE_TRACEME");
 183
 184                 printf("\tChild will make one syscall\n");
 185                 raise(SIGSTOP);
 186
 187                 syscall(SYS_gettid, 10, 11, 12, 13, 14, 15);
 188                 _exit(0);
 189         }
 190
 191         int status;
 192
 193         /* Wait for SIGSTOP. */
 194         if (waitpid(chld, &status, 0) != chld || !WIFSTOPPED(status))
 195                 err(1, "waitpid");
 196
 197         struct user_regs_struct regs;
 198
 199         printf("[RUN]\tSYSEMU\n");
 200         if (ptrace(PTRACE_SYSEMU, chld, 0, 0) != 0)
 201                 err(1, "PTRACE_SYSEMU");
 202         wait_trap(chld);
 203
 204         if (ptrace(PTRACE_GETREGS, chld, 0, &regs) != 0)
 205                 err(1, "PTRACE_GETREGS");
 206
 207         if (regs.user_syscall_nr != SYS_gettid ||
 208             regs.user_arg0 != 10 || regs.user_arg1 != 11 ||
 209             regs.user_arg2 != 12 || regs.user_arg3 != 13 ||
 210             regs.user_arg4 != 14 || regs.user_arg5 != 15) {
 211                 printf("[FAIL]\tInitial args are wrong (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
 212                 nerrs++;
 213         } else {
 214                 printf("[OK]\tInitial nr and args are correct\n");
 215         }
 216
 217         printf("[RUN]\tRestart the syscall (ip = 0x%lx)\n",
 218                (unsigned long)regs.user_ip);
 219
 220         /*
 221          * This does exactly what it appears to do if syscall is int80 or
 222          * SYSCALL64.  For SYSCALL32 or SYSENTER, though, this is highly
 223          * magical.  It needs to work so that ptrace and syscall restart
 224          * work as expected.
 225          */
 226         regs.user_ax = regs.user_syscall_nr;
 227         regs.user_ip -= 2;
 228         if (ptrace(PTRACE_SETREGS, chld, 0, &regs) != 0)
 229                 err(1, "PTRACE_SETREGS");
 230
 231         if (ptrace(PTRACE_SYSEMU, chld, 0, 0) != 0)
 232                 err(1, "PTRACE_SYSEMU");
 233         wait_trap(chld);
 234
 235         if (ptrace(PTRACE_GETREGS, chld, 0, &regs) != 0)
 236                 err(1, "PTRACE_GETREGS");
 237
 238         if (regs.user_syscall_nr != SYS_gettid ||
 239             regs.user_arg0 != 10 || regs.user_arg1 != 11 ||
 240             regs.user_arg2 != 12 || regs.user_arg3 != 13 ||
 241             regs.user_arg4 != 14 || regs.user_arg5 != 15) {
 242                 printf("[FAIL]\tRestart nr or args are wrong (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
 243                 nerrs++;
 244         } else {
 245                 printf("[OK]\tRestarted nr and args are correct\n");
 246         }
 247
 248         printf("[RUN]\tChange nr and args and restart the syscall (ip = 0x%lx)\n",
 249                (unsigned long)regs.user_ip);
 250
 251         regs.user_ax = SYS_getpid;
 252         regs.user_arg0 = 20;
 253         regs.user_arg1 = 21;
 254         regs.user_arg2 = 22;
 255         regs.user_arg3 = 23;
 256         regs.user_arg4 = 24;
 257         regs.user_arg5 = 25;
 258         regs.user_ip -= 2;
 259
 260         if (ptrace(PTRACE_SETREGS, chld, 0, &regs) != 0)
 261                 err(1, "PTRACE_SETREGS");
 262
 263         if (ptrace(PTRACE_SYSEMU, chld, 0, 0) != 0)
 264                 err(1, "PTRACE_SYSEMU");
 265         wait_trap(chld);
 266
 267         if (ptrace(PTRACE_GETREGS, chld, 0, &regs) != 0)
 268                 err(1, "PTRACE_GETREGS");
 269
 270         if (regs.user_syscall_nr != SYS_getpid ||
 271             regs.user_arg0 != 20 || regs.user_arg1 != 21 || regs.user_arg2 != 22 ||
 272             regs.user_arg3 != 23 || regs.user_arg4 != 24 || regs.user_arg5 != 25) {
 273                 printf("[FAIL]\tRestart nr or args are wrong (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
 274                 nerrs++;
 275         } else {
 276                 printf("[OK]\tReplacement nr and args are correct\n");
 277         }
 278
 279         if (ptrace(PTRACE_CONT, chld, 0, 0) != 0)
 280                 err(1, "PTRACE_CONT");
 281         if (waitpid(chld, &status, 0) != chld)
 282                 err(1, "waitpid");
 283         if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
 284                 printf("[FAIL]\tChild failed\n");
 285                 nerrs++;
 286         } else {
 287                 printf("[OK]\tChild exited cleanly\n");
 288         }
 289 }
 290
 291 static void test_restart_under_ptrace(void)
 292 {
 293         printf("[RUN]\tkernel syscall restart under ptrace\n");
 294         pid_t chld = fork();
 295         if (chld < 0)
 296                 err(1, "fork");
 297
 298         if (chld == 0) {
 299                 if (ptrace(PTRACE_TRACEME, 0, 0, 0) != 0)
 300                         err(1, "PTRACE_TRACEME");
 301
 302                 printf("\tChild will take a nap until signaled\n");
 303                 setsigign(SIGUSR1, SA_RESTART);
 304                 raise(SIGSTOP);
 305
 306                 syscall(SYS_pause, 0, 0, 0, 0, 0, 0);
 307                 _exit(0);
 308         }
 309
 310         int status;
 311
 312         /* Wait for SIGSTOP. */
 313         if (waitpid(chld, &status, 0) != chld || !WIFSTOPPED(status))
 314                 err(1, "waitpid");
 315
 316         struct user_regs_struct regs;
 317
 318         printf("[RUN]\tSYSCALL\n");
 319         if (ptrace(PTRACE_SYSCALL, chld, 0, 0) != 0)
 320                 err(1, "PTRACE_SYSCALL");
 321         wait_trap(chld);
 322
 323         /* We should be stopped at pause(2) entry. */
 324
 325         if (ptrace(PTRACE_GETREGS, chld, 0, &regs) != 0)
 326                 err(1, "PTRACE_GETREGS");
 327
 328         if (regs.user_syscall_nr != SYS_pause ||
 329             regs.user_arg0 != 0 || regs.user_arg1 != 0 ||
 330             regs.user_arg2 != 0 || regs.user_arg3 != 0 ||
 331             regs.user_arg4 != 0 || regs.user_arg5 != 0) {
 332                 printf("[FAIL]\tInitial args are wrong (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
 333                 nerrs++;
 334         } else {
 335                 printf("[OK]\tInitial nr and args are correct\n");
 336         }
 337
 338         /* Interrupt it. */
 339         kill(chld, SIGUSR1);
 340
 341         /* Advance.  We should be stopped at exit. */
 342         printf("[RUN]\tSYSCALL\n");
 343         if (ptrace(PTRACE_SYSCALL, chld, 0, 0) != 0)
 344                 err(1, "PTRACE_SYSCALL");
 345         wait_trap(chld);
 346
 347         if (ptrace(PTRACE_GETREGS, chld, 0, &regs) != 0)
 348                 err(1, "PTRACE_GETREGS");
 349
 350         if (regs.user_syscall_nr != SYS_pause ||
 351             regs.user_arg0 != 0 || regs.user_arg1 != 0 ||
 352             regs.user_arg2 != 0 || regs.user_arg3 != 0 ||
 353             regs.user_arg4 != 0 || regs.user_arg5 != 0) {
 354                 printf("[FAIL]\tArgs after SIGUSR1 are wrong (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
 355                 nerrs++;
 356         } else {
 357                 printf("[OK]\tArgs after SIGUSR1 are correct (ax = %ld)\n",
 358                        (long)regs.user_ax);
 359         }
 360
 361         /* Poke the regs back in.  This must not break anything. */
 362         if (ptrace(PTRACE_SETREGS, chld, 0, &regs) != 0)
 363                 err(1, "PTRACE_SETREGS");
 364
 365         /* Catch the (ignored) SIGUSR1. */
 366         if (ptrace(PTRACE_CONT, chld, 0, 0) != 0)
 367                 err(1, "PTRACE_CONT");
 368         if (waitpid(chld, &status, 0) != chld)
 369                 err(1, "waitpid");
 370         if (!WIFSTOPPED(status)) {
 371                 printf("[FAIL]\tChild was stopped for SIGUSR1 (status = 0x%x)\n", status);
 372                 nerrs++;
 373         } else {
 374                 printf("[OK]\tChild got SIGUSR1\n");
 375         }
 376
 377         /* The next event should be pause(2) again. */
 378         printf("[RUN]\tStep again\n");
 379         if (ptrace(PTRACE_SYSCALL, chld, 0, 0) != 0)
 380                 err(1, "PTRACE_SYSCALL");
 381         wait_trap(chld);
 382
 383         /* We should be stopped at pause(2) entry. */
 384
 385         if (ptrace(PTRACE_GETREGS, chld, 0, &regs) != 0)
 386                 err(1, "PTRACE_GETREGS");
 387
 388         if (regs.user_syscall_nr != SYS_pause ||
 389             regs.user_arg0 != 0 || regs.user_arg1 != 0 ||
 390             regs.user_arg2 != 0 || regs.user_arg3 != 0 ||
 391             regs.user_arg4 != 0 || regs.user_arg5 != 0) {
 392                 printf("[FAIL]\tpause did not restart (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
 393                 nerrs++;
 394         } else {
 395                 printf("[OK]\tpause(2) restarted correctly\n");
 396         }
 397
 398         /* Kill it. */
 399         kill(chld, SIGKILL);
 400         if (waitpid(chld, &status, 0) != chld)
 401                 err(1, "waitpid");
 402 }
 403
 404 int main()
 405 {
 406         printf("[RUN]\tCheck int80 return regs\n");
 407         test_sys32_regs(do_full_int80);
 408
 409 #if defined(__i386__) && (!defined(__GLIBC__) || __GLIBC__ > 2 || __GLIBC_MINOR__ >= 16)
 410         vsyscall32 = (void *)getauxval(AT_SYSINFO);
 411         printf("[RUN]\tCheck AT_SYSINFO return regs\n");
 412         test_sys32_regs(do_full_vsyscall32);
 413 #endif
 414
 415         test_ptrace_syscall_restart();
 416
 417         test_restart_under_ptrace();
 418
 419         return 0;
 420 }